#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <sys/time.h>

/*
 * 获取1970~1980之间十年的秒数
 */


void set_current_time()
{
  struct tm tm;

  tm.tm_year = 2017-1900;
  tm.tm_mon = 11;
  tm.tm_mday = 23;
  tm.tm_hour = 14;
  tm.tm_min = 17;
  tm.tm_sec = 0;

  time_t now = mktime(&tm);

  printf("time()->localtime()->mktime() : %d\n", (int)now);
  
  stime(&now);
}

void ten_year_second()
{
  time_t timep;
  struct tm * p;

  time(&timep);
  printf("time() : %ld\n", timep);
  
  p = localtime(&timep);
  timep = mktime(p);
  
  printf("time()->localtime()->mktime() : %d\n", (int)timep); 
}

/* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
 *
 * [For the Julian calendar (which was used in Russia before 1917,
 * Britain & colonies before 1752, anywhere else before 1582,
 * and is still in use by some communities) leave out the
 * -year/100+year/400 terms, and add 10.]
 *
 * This algorithm was first published by Gauss (I think).
 *
 * WARNING: this function will overflow on 2106-02-07 06:28:16 on
 * machines where long is 32-bit! (However, as time_t is signed, we
 * will already get problems at other places on 2038-01-19 03:14:08)
 */

unsigned long
mktime_system(const unsigned int year0, const unsigned int mon0,
       const unsigned int day, const unsigned int hour,
       const unsigned int min, const unsigned int sec)
{
	unsigned int mon = mon0, year = year0;

	/* 1..12 -> 11,12,1..10 */
	if (0 >= (int) (mon -= 2)) {
		mon += 12;	/* Puts Feb last since it has leap day */
		year -= 1;
	}

	return ((((unsigned long)
		  (year/4 - year/100 + year/400 + 367*mon/12 + day) +
		  year*365 - 719499
	    )*24 + hour /* now have hours */
	  )*60 + min /* now have minutes */
	)*60 + sec; /* finally seconds */
}

void main()
{
	set_current_time();
	ten_year_second();

	printf("ten:%ld\n", mktime_system(1980, 1, 1, 0, 0, 0));
	printf("ten:%ld\n", mktime_system(1979, 12, 31, 23, 59, 59));
}




